Download COS 318: Operating Systems Introduction Andy Bavier Computer Science Department

COS 318: Operating Systems
Introduction
Andy Bavier
Computer Science Department
Princeton University
http://www.cs.princeton.edu/courses/archive/fall10/cos318/
Today
Course staff and logistics
  What is an operating system?
  Evolution of computing and operating systems
  Why study operating systems?
  What’s in COS318?
 
2
Course Staff and Logistics
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Instructor
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Andy Bavier, 212 CS Building, [email protected]
Office hours: Tue 3-5pm
Teaching Assistants
Prem Gopalan, [email protected]
Office hours: Fri 10am-noon
  Dominic Kao, [email protected]
Office hours: Fri 11am-1pm
 
 
Information
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Website:
•  http://www.cs.princeton.edu/courses/archive/fall10/cos318/
 
Subscribe to [email protected]
3
Resolve “TBD”
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Regular precept
Time: Tuesday 7:30pm – 8:30pm
  Location: default is this room, CS 105
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Review of x86 Real-Mode Assembly
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Monday Sep. 20, 7:30pm – 8:30pm
Design review
Monday Sep. 27, 5pm -- 9pm
  Sign up online
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4
COS318 in Systems Course Sequence
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Prerequisites
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300-400 courses in systems
 
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COS 217: Introduction to Programming Systems
COS 226: Algorithms and Data Structures
COS318: Operating Systems
COS320: Compiler Techniques
COS333: Advanced Programming Techniques
COS425: Database Systems
COS471: Computer Architecture
Courses needing COS318
 
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COS 461: Computer Networks
COS 518: Advanced Operating Systems
COS 561: Advanced Computer Networks
5
Course Materials
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Textbook
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Lecture notes
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Available on website
Precept notes
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Modern Operating Systems, 3rd Edition, Andrew S.
Tanenbaum
Available on website
Other resources – on website
6
Exams, Participation and Grading
 
Grading
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50% with extra points
20%
20%
10%
Midterm Exam
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First 5 projects:
Midterm:
Final project:
Reading & participation:
Test lecture materials and projects
Tentatively scheduled on Thursday of the midterm week
Reading and participation
 
 
 
Submit your reading notes BEFORE each lecture
Sign-in sheet at each lecture
Grading (3: excellent, 2: good, 1: poor, 0: none)
7
The First 5 Projects
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Projects
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How
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Bootup (150-300 lines)
Non-preemptive kernel (200-250 lines)
Preemptive kernel (100-150 lines)
Interprocess communication and driver (300-350 lines)
Android OS (??? lines)
Pair up with a partner, will change after 3 projects
Each project takes two weeks
Design review at the end of week one
All projects due Mondays 11:59pm
The Lab
 
 
Linux cluster in 010 Friends Center, a good place to be
You can setup your own Linux PC to do projects
8
Project Grading
 
Design Review
Signup online for appointments
  10 minutes with the TA in charge
  0-5 points for each design review
  10% deduction if missing the appointment
 
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Project completion
10 points for each project
  Extra points available
 
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Late policy of grading projects
1 hour: 98.6%, 6 hours: 92%, 1 day: 71.7%
  3 days: 36.8%, 7 days: 9.7%
 
9
Final Project
A simple file system
  Grading (20 points)
  Do it alone
  Due on Dean’s date (~3 weeks)
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10
Things To Do
  Do
not put your code or designs or thoughts
on the Web
Other schools are using similar projects
  Not even on Facebook or the like
 
Follow Honor System: ask when unsure, cooperation OK
but work is your own (or in pairs for projects)
  For today’s material:
 
 
 
Read MOS 1.1-1.3
For next time
 
Read MOS 1.4-1.5
11
Email to [email protected]
Name
  Year
  Major
  Why you’re taking the class
  What you’d like to learn
 
12
Today
Course staff and logistics
  What is an operating system?
  Evolution of computing and operating systems
  Why study operating systems?
  What’s in COS318?
 
13
What Is an Operating System?
gcc
vi
Browser
DVD Player
Operating System
Hardware
 
Software that sits between applications and hardware
 
Also between different applications and different users
Has privileged access to hardware
  Provides services and interfaces to applications
User applications call OS routines for access and services
 
14
What Does an Operating System Do?
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Provides a layer of abstraction for hardware resources
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Allows user programs to deal with higher-level, simpler,
and more portable concepts than the raw hardware
•  E.g., files rather than disk blocks
 
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Makes finite resources seem “infinite”
Manages the resources
Manage complex resources and their interactions for an
application
  Allow multiple applications to share resources without
hurting one another
  Allow multiple users to share resources without hurting
one another
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15
Abstraction
How to handle complexity
  Hide underlying details, and provide cleaner, easier-touse, more elegant concepts and interfaces
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Also provides standardized interfaces despite diversity of
implementation underneath
A key to understanding Operating Systems
  A key principle in Computer Science
 
16
Example of Abstraction: Disk
 
Disk hardware and operations are very complex
Multiple heads, cylinders, sectors, segments
  Have to wait for physical movement before writing or
reading data to/from disk
  Data stored discontiguously for performance, reliability
  To read or write simple data would take a lot of
coordination if dealing with the hardware directly
  Sizes and speeds are different on different computers
 
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OS provides simple read() and write() calls as the
application programmer’s interface (API)
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Manages the complexity transparently, in conjunction
with the disk controller hardware
17
Example of Abstraction: Networks
 
Data communicated from one computer to another are:
Broken into fragments that are sent separately, and
arrive at different times and out of order
  Waited for and assembled at the destination
  Sometimes lost, so fragments have to be resent
  An application programmer doesn’t want to manage this
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OS provides a simple send() and receive() interface
 
Takes care of the complexity, in conjunction with the
networking hardware
18
Resource Management
Allocation
  Virtualization
  Reclamation
  Protection
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Resource Allocation
Computer has finite resources
  Different applications and users compete for them
  OS dynamically manages which applications get how
many resources
  Multiplex resources in space and time
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Time multiplexing: CPU, network
  Space multiplexing: disk, memory
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E.g., what if an application runs an infinite loop?
while (1);
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Resource Virtualization
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OS gives each program the illusion of effectively
infinite, private resources
“infinite” memory (by backing up to disk)
  CPU (by time-sharing)
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Resource Reclamation
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The OS giveth, and the OS taketh away
Voluntary or involuntary at runtime
  Implied at program termination
  Cooperative
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22
Protection
You can’t hurt me, I can’t hurt you
  OS provides safety and security
  Protects programs and their data from one another, as
well as users from one another
  E.g., what if I could modify your data, either on disk or
while your program was running?
 
23
Mechanism vs. policy
Mechanisms are tools or vehicles to implement policies
  Examples of policies:
 
All users should be treated equally
  Preferred users should be treated better
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Today
Course staff and logistics
  What is an operating system?
  Evolution of computing and operating systems
  Why study operating systems?
  What’s in COS318?
 
25
A Typical Academic Computer (1988 vs. 2008)
1988
2008
Ratio
Intel CPU transistors
0.5M
1.9B
~4000x
Intel CPU core x clock
10Mhz
4×2.66Ghz
~1000x
DRAM
2MB
16GB
8000x
Disk
40MB
1TB
25,000x
Network BW
10Mbits/sec
10GBits/sec
1000x
Address bits
32
64
2x
Users/machine
10s
<1
>10x
$/machine
$30K
$3K
1/10x
$/Mhz
$30,000/10
$3,000/10,000
1/10,000x
26
Computing and Communications
Exponential Growth! (Courtesy Jim Gray)
Performance/Price doubles every 18 months
  100x per decade
  Progress in next 18 months
= ALL previous progress
 
New storage = sum of all old storage (ever)
  New processing = sum of all old processing.
 
 
This has led to some broad phases in computing,
and correspondingly in operating systems
15 years ago
27
Phase 1: Batch Systems
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Hardware very expensive, only one user at a time
Batch processing: load, run, print
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Problem: better system utilization
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OS linked in as a subroutine library
System idle when job waiting for I/O
Development: multiprogramming
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Multiple jobs resident in computer’s memory
Hardware switches between them (interrupts)
Memory protection: keep bugs to individual programs
Application
OS
Hardware
hardware
28
Phase 2: Time Sharing
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Problem: batch jobs hard to debug
Use cheap terminals to share a computer interactively
MULTICS: designed in 1963, run in 1969
Shortly after, Unix enters the mainstream
Issue: thrashing as the number of users increases
App1
App2
...
App2
Time-sharing OS
Hardware
hardware
29
Phase 3: Personal Computer
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Personal computer
Altos OS, Ethernet, Bitmap display, laser printer
  Pop-menu window interface, email, publishing SW,
spreadsheet, FTP, Telnet
  Eventually >100M units per year
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PC operating system
Memory protection
  Multiprogramming
  Networking
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30
Now: > 1 Machines per User
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Pervasive computers
Wearable computers
  Communication devices
  Entertainment equipment
  Computerized vehicle
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OS are specialized
Embedded OS
  Specially configured generalpurpose OS
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31
Now: Multiple Processors per Machine
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Multiprocessors
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Multicomputers
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SMP: Symmetric MultiProcessor
ccNUMA: Cache-Coherent Non-Uniform
Memory Access
General-purpose, single-image OS with
multiproccesor support
Supercomputer with many CPUs and highspeed communication
Specialized OS with special messagepassing support
Clusters
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A network of PCs
Commodity OS
32
Trend: Multiple “Cores” per Processor
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Multicore or Manycore transition
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Intel and AMD have released 4-core CPUs
SUN’s Niagara processor has 8-cores
Azul packed 24-cores onto the same chip
Intel has a TFlop-chip with 80 cores
Accelerated need for software support
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OS support for manycores
Parallel programming of applications
33
Today
Course staff and logistics
  What is an operating system?
  Evolution of computing and operating systems
  Why study operating systems?
  What’s in COS318?
 
34
Why Study OS?
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OS is a key part of a computer system
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Learn about concurrency
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It makes our life better (or worse)
It is “magic” to realize what we want
It gives us “power”
Parallel programs run on OS
OS runs on parallel hardware
Best way to learn concurrent programming
Understand how a system works
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How many procedures does a key stroke invoke?
What happens when your application references 0 as a pointer?
Building a small OS will go a long way…
35
Why Study OS?
 
Important for studying other areas
 
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Networking, distributed systems, …
Full employment
New hardware capabilities and organizations
  New features
  New approaches
  Engineering tradeoffs keep shifting as the hardware
changes below and the apps change above
 
36
Today
Course staff and logistics
  What is an operating system?
  Evolution of computing and operating systems
  Why study operating systems?
  What’s in COS318?
 
37
What’s in COS 318?
 
Methodology
 
 
 
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Lectures with discussions
Readings with topics
Six projects to build a small but real OS, play with Android
Covered concepts
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Operating system structure
•  Processes, threads, system calls and virtual machine monitor
 
Synchronization
•  Mutex, semaphores and monitors
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I/O subsystems
•  Device drivers, IPC, and introduction to networking
 
Virtual memory
•  Address spaces and paging
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Storage system
•  Disks and file system
38
What is COS 318 Like?
 
Is it theoretical or practical?
Focus on concepts, also getting hands dirty in projects
  Engineering tradeoffs: requirements, constraints,
optimizations, imperfections
  High rate of change in the field yet lots of inertia in OSs
 
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Is it easy?
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No. Fast-paced, hard material, a lot of programming
What will help me succeed?
Solid C background, pre-reqs, tradeoff thinking
  NOT schedule overload
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39